Stabilized compositions

ABSTRACT

ORGANIC MATERIALS, PARTICULARLY SYNTHETIC POLYMERS SUCH AS POLYPROPYLENE, ARE PROTECTED AGAINST OXIDATION IN AIR, THERMAL DEGRADATION OR DETERIORATION BY INCLUDING, IN SUCH SUBSTANCES, A STABILIZING AMOUNT OF AN ANTIOXIDANT. THE ANTIOXIDANT IS OBTAINED BY REACTING (A) AN A,B-UNSATURATED ETHER OF A HINDERED HYROQUINONE AND (B) A PHOSPHINODITHIOIC ACID OR A O,O-DIESTER OF PHOSPHOROTHIOLOTHIONIC ACID.

United States Patent 3,753,945 STABILIZED COMPOSITIONS Eduard K.Kleiner, Dobbs Ferry, N.Y., assignor to Ciba-Geigy Corporation NoDrawing. Original application Jan. 31, 1969, Ser. No. 795,696, nowPatent No. 3,639,538, dated Feb. 1, 1972. Divided and this applicationMar. 12, 1971, Ser. No.

Int. Cl. C081? /58; C08g 51/58 US. Cl. 26045.85 H 8 Claims ABSTRACT OFTHE DISCLOSURE The present invention is concerned with novel compoundswhich are useful as antioxidants for organic materials and particularly,as antioxidants for synthetic polymers such as, for example,polypropylene, polyethylene, polyesters, polystyrene, polyvinylchloride,nylon and other polyamides, cellulosics, polyacetals, polyurethanes,petroleum and wood resins, mineral oils, animal and vegetable fats,waxes, rubbers such as styrene-butadiene rubber (SBR),acrylonitrile-butadiene-styrene rubber (ABS), olefin-copolymers,ethylene-vinyl-acetate copolymers, polycarbonates, polyacrylonitrile,poly(4-methyl pentene-l) polymers, polyoxymethylenes, and the like. Thepresent invention also relates to a novel procedure for preparing theaforesaid novel antioxidants and to stabilized compositions containingsaid novel antioxidants.

The prevention of oxidation of various organic materials is obviously ofprimary industrial concern and therefore, antioxidants are used in oradded to a wide variety of commercial products such as syntheticpolymers of the type indicated supra, oils, plastic materials, etc.,which are normally subject to oxidative deterioration.

The novel antioxidants of the present invention are represented by thefollowing formula:

2 0 OR (Formula I) wherein -Q is R or -OR -R is (l'ower) alkyl (lower)alkyl --R -R -R are each hydrogen, lower alkyl, phenyl,

aralkyl 0r C -H COOR, where m is 0 to 6 3,753,945 Patented Aug. 21, 1973-R is alkyl, cycloalkyl, phenyl, aralkyl and when Q is OR the two Rgroups can be --(CH where n is 2 or 3, forming a cyclic 0,0-diester ofphosphorothiolothionic acid.

As used herein, alkyl covers groups having from 1 to 24 carbon atoms,and preferably from 1 to 12 carbon atoms. Illustrative examples of suchgroups are methyl, ethyl, isopropyl, n-butyl, t-butyl, n-hexyl, n-octyl,n-decyl, n-dodecyl, n-hexadecyl, eicosyl, tetraeicosyl and the variousbranched chain isomers thereof. By lower alkyl is meant alkyl groupshaving from 1 to 6 carbon atoms. Cycloalkyl includes cycloalkyl groupshaving up to 6 carbon atoms, such as cyclobutyl, cyclopentyl,cyclohexyl. Aralkyl covers phenyl substituted alkyl groups having up to24 carbon atoms. In addition to alkyl substitution the phenyl groups mayalso be substituted chlorine, bromine, alkoxy, hydroxyl, alkylthio or acarboalkoxy group. Illus trative examples of aralkyl groups are benzyl,phenylethyl, 2,4-dibutylphenyl, 2,4,6-trihexylphenyl, 2-chloroto1yl, 4-hydroxy 3 methylphenyl, 4-ethoxyphenyl, 4-butylhtiophenyl,4-ethoxyphenyl, 4-butylthiophenyl, 3-hydroXy-4- ethylthiophenyl and thelike. Where R R or R is -C H m is O to 6, but preferably 0 or 1.

The novel antioxidants of the present invention are the additionproducts of (a) an a, 3-unsaturaetd ester of hindered hydroquinone ofthe formula and (b) a phosphinodithioic acid or a 0,0-diester of aphosphorothiolothionic acid of the formulae respectively, wherein R, R RR R are as defined above. The addition reaction involving the 01,3-unsaturated ester and a phosphinodithioic acid or a 0,0- diester of aphosphorothiolothionic acid is effected by heating equivalent amounts ofthe reactions in an inert solvent at temperatures from about 30 to about100 C. as described in Houben-Weyl, Methoden der Organischen Chemie,vol. XII/l (1963) page 284 and vol. XII/2 (1964), page 683 (Georg ThiemeVerlag, Stuttgart). A catalytic amount of base may be used to speed upthe condensation reaction, especially if lower condensation temperaturesare employed. Preferred bases are alkoxides such as sodium or potassiummethoxide or ethoxide, organic bases such as piperidine, triethylamine,picoline or benzyltn'methylammonium hydroxide and the like.

'The novel antioxidants of this invention were prepared by using thefollowing general procedure:

Equimolar amounts of the c b-unsaturated ester and the phosphinodithioicacid or 0,0-diester of a phosphorothiolothionic acid are dissolved in 2to 3 times the amount of chloroform or benzene and sealed undernitrogen. The reaction vessel is kept at about C. for 12 to 20 hoursuntil the conversion is complete as checked by thin layerchromatography. The reaction mixture is then washed with a saturatedsodium bicarbonate solution and Water, and then dried over sodiumsulfate. Then the solvent is evaporated and the crude product purifiedeither by distillation or by crystallization or by filtering thesolution through neutral aluminum oxide. Yields are high, that is,generally over 80% Illustrative coo-unsaturated esters used in preparingthe antioxidants of the present invention as indicated above, arerepresented by the following formula:

R C O R wherein -R is (lower) alkyl (lower) alkyl and R R and R are asdefined above. Examples of such esters are:

Esters of- R R2 R3 Acrylic acid H --H H Methacrylic acid H -H -CHaGrotonic acid CH3 H --H Cinnamic acid -CsH5 -H -H Maleic acid- H -C 00 R-H Mesaconic aci C0O R H -CHz Citraconic acid COOR -CHa It-acouic acid HCH2COO R Aconitic acid -COO R --H C H2000 R The preferreda,/8-unsaturated esters are esters of acrylic acid, fumaric and itaconicacid. The preferred phosphinodithioic acid used in preparingantioxidants represented by Formula I where Q is R aredialkylphosphinodithioic acids such as diphenylanddibenzylphosphinodithioic acids.

Illustrative examples of phosphinodithioic acids are and the like. Thesephosphinodithioic acids are well known and are described in Houbenheyl,ibid., vol. XH/l (1963), pages 269-272.

The preferred 0,0diesters of phosphorothiolothionic acid used inpreparing antioxidants represented by Formula I Where -Q is O'R are thedialkylesters with straight or branched chain alkyl groups having from 1to 18 carbon atoms, diphenyl and diaralkylesters.

Illustrative examples of '0,0-diesters of phosphorothiolothionic acidsare 0,0-dimethyl hydrogen phosphorodithioate; 0,0-diisopropyl hydrogenphosphorodithioate; 0,0-di-n-pentyl hydrogen phosphorodithioate;0,0-di-noctyl hydrogen phosphorodithioate; 0,0-di-n-dodecyl hydrogenphosphorodithioate; 0,0-di-n-octadecyl hydrogen phosphorodithioate;0,0-diphenyl hydrogen phosphorodithioate; 0,0-dibenzy1 hydrogenphosphorodithioate; 0,0- bis(2-phenylethyl) hydrogen phosphorodithioate;0,0- bis(4-methy1phenyl) hydrogen phosphorodithioate; 0,0-bis(3,4-di-t-butylphenyl) hydrogen phosphorodithioate, cyclic0,0-diesters of phosphorothiolothionic acids such as 2mercapto-Z-thionol,3,2-dioxaphospholane, 2 mercapto 2 thiono 4,5dimethyl 1,3,2-dioxaphospholane and the like. These QO-diesters ofphosphorothiolothionic acids are well known and are described in Houbeu-Weyl, ibid., vol. XII/2 (1964), pages 683-689.

Some of the preferred starting a,,8-unsaturated ester compounds used inpreparing the antioxidant compounds of the present invention are asfollows:

(a) 3,5-di-tert-butyl-4-hydroxyphenyl acrylate CH =CHCOOR (b) 3,5-di-tert-butyl-4-hydroxyphenyl methacrylate CH =C(CH )COOR (c) bis(3,5-di-tert-butyl-4-hydroxyphenyl) fumarate H COORo COORo H (d)bis(3,S-di-tert-butyl-4-hydroxyphenyl) itaconate wherein R is I Hs)a 3):

The above listed a 's-unsaturated esters were reacted with the followingphosphinodithioic acids and 0,0-diesters of phosphorothiol-othionicacid:

ethyl hydrogen phosphorodithioate to the 0a,}3-lll'l8filZ-l1l'fli6dester according to the general procedure described above.

Appearance lized Irom Melting or boiling point 0.) crystal- Startingmaterials Product Slightly yellow viscous oil. Purified by Aluminumoxide chroma- (a) plus (e) 3,5-di-t-butyl-4-hydroxyphenyl,3-(diphenylphosphinothio- (A) tography. thi0)propionate,RQOCOOHZCH2S(S)P(CBH5)2. White powder M.P., 117-119 cyclohexane (c) plus(e).. Bis(3-5-di-t-butyl-4-hydr0xyphenyl), Z-(rliphenylphos- (B)phinothioylthio)succinate.

R OCOCHS(S)P(CcH5)g ROOCOCH? Do M.P.,5456 heptane/cyclohexane (d) plus(e) Bis(3,5-di-t-butyl-4'hydroxyphenyl) 2-(diphenylphosphin- (C)othioylthiomethyDsuccinate.

ROCOCHCHzS(S)P(CaH )g RoOCOCHi Colorless, viscous oil Purified byaluminum oxide chroma- (b) plus (i) 3,5-di-t-butyl4-hydroxyphenylZ-methyl-Ii-(diethoxyphos- (D) tography. p hingtlI11io)ylthio)propionateROOCOOH(CH3)OH,S(S)

2 5 2- White crystals M.P., 80-85 hexane-; (0) plus (i)...Bis(3,5-di-t-butyl-4-hydroxyphenyl), 2-(diethoxyphos- (E)phinothioylthio)suecinate.

R00 00 CHS(S)P(OC:H )2

ROOCOCH2 D0 M.P.,57-61 ((1) plus (i)-Bis(3,5-di-t-butyl-4-hydroxyphenyl) 2-(diethoxyphos- (F) phinothioylthiomethyl)succinate.

R00 00 OHCHzS (S)P(O C211 R00 00 CH:

One general method for preparing said unsaturated esters comprisesreacting an alcohol dissolved in pyridine with an acid chloride. Forexample 2,6-di-t-butylhydroquinone and acrylyl chloride yield3,5-di-t-butyl-4-hydroxyphenyl acrylate; 2,6-di-t-butylhydroquinone andmethacrylyl chloride yield 3,5-di-t-butyl-4-hydroxyphenyl methacrylate;2,6-di-t-butylhydroquinone and fumaryl chloride yieldbis(3,5-t-butyl-4-hydroxypheny1)fumarate;

4 2,G-di-t-butylhydroquinone and itaconyl chloride yield bis (3,S-di-tbutyl-4-hydroxyphenyl) itaconate.

TABLE II.NOVEL ANTIOXIDANTS Phosphinodithioic acids and 0,0-diesters ofphosphorothiolothionic acids a,fl-Unsaturated esters 1 Novelantioxidants CH PSSH ROCOCHSS)PCH G a 5): K D)2 a 2 sh R 0 0 O OH:

CH) P(S SH R OCOCHS(S)P(C H H 2 2011000110): (trans) 4 R00 C 0 CH:

(C5H CH2)zP(S)SH CH2=CHCOOR R00O0CH2CH2$(S)P(CH2CBH5)1 (I)(p-OH3CuH-i)aP(S)SH OH2=CHC0OR ROOCOOHiCHzS(S)P(CaH4CH )1 (J)(p-ClCcH4)zP(S)SH CHz=C-C O 0 R R 0 C O OHCHzS (S)P(CH4Cl)g (K) CHzCOORR OCOCHZ (OH O)PSSH ROOCOCHS(SPOCH L 5 n 2 )2 5 11):

\ R00 0 0 CH:

(C H O) P(S)SH R OCOCHS(S)P(OC H) M 5 c11oooR)2 (trans) 5 R 0 0 0 CH;

(OeH CH2O)2P (S)SH CH2=C (CH3)COORO RoOCOCH(CH3)CH2S (S)P(O CHzCsHs):(N) (C5H5CH2CH2O)2P (S)SH CH1=CHCOOR R00COCH2CH2S(S)P(OCHzCHgCeHa): (O)CH2O 0Hi o-oooRo /0CH1 (P) P(S)SH CHZCOORQ RQOCOCHCHzS(S) P CH -O ROCOCHQ O-GHz CH CHO CHg=C--COOR0 /OCHCH; P(S)SH CHzCOORO R OCOCHCH2S(S)PCH;OHO ROOOOCHz O-GH-CH C (0113):, 3,5-di-t-butyl-4-hydroxyphenyl.

1 Ro= OH After the precipitated hydrochloride is removed, the reactionliquid is evaporated yielding crude product which is purified either bydistillation or recrystallization.

The oxidation of most polymers is so slow at ambient temperatures, evenin the absence of antioxidants, that testing of the effects ofantioxidants must necessarily be conducted at high temperatures in orderto yield results within a convenient period of time. The tests conductedon the materials listed in the following tables were conducted either ina tubular oven with an airflow of 400 cubic feet per minute at an oventemperature of 150 C. or in a rotary oven with a 4 r.p.m. at an oventemperature of 150 C. The oven ageing is set out in hours.

In preparing the sample for testing, unstabilized polypropylene powderis thoroughly blended with the indicated antioxidant. The blendedmaterial is thereafter milled on a two-roller mill at a temperature of182 C. for six minutes after which time the stabilized polypropylene issheeted from the mill and allowed to cool. The milled polypropylenesheet which has been stabilized is then cut into small pieces andpressed for seven minutes on a hydraulic press at 218 C. and 174 p.s.i.pressure. The resultant sheet of 25 mil thickness is then tested forresistance to accelerated ageing in the above described tubular oven. InTables III and IV are reported the results of the oven ageing tests inwhich the antioxidants of this invention were added to polypropylenetogether with the indicated ultraviolet light absorber and thesynergist.

TABLE III.EVALUATION OF ANTIOXIDANTS IN POLY- PROPYLENE (25 MIL), ROTARYOVEN, 150 C.

Hours to fail at 0.17 antio idant 0.25% antiplus 0.5% 101x182; U.V.20p3l171 s us Product p U.v.-% Ds'rD NOTE.UV2:An ultraviolet absorber,2(3',5'-di-tert-butyl-2-hydroxy-phenyl)-5-ch1orobenzotriazole.DSTDPzdistearylthiodipropionate, commercial synergist for antioxidants.

TABLE IV.EVALUATION OF AN'IIOXIDANTS IN POLY PROPYLENE (25 MIL), TUBULAROVEN, 150 C.

Hours to fail at- 0.17 antioi iidant 25% antlplus 0.5% loxigiggt .V-2Op:l3i 17s us Product p U.v.- DSTDI See footnote bottom of Table III.

Results similar to those reported in Tables HI and IV are obtained whenthe antioxidants of Table II are em played together with the indicatedsecondary antioxidants and ultraviolet absorbers.

phenyl) benzotriazole.

No'rE.DLTDP=Dilaurylthiodipropionate.

It should be noted that in all above examples of stabilizingcompositions the use of a secondary antioxidant and an ultravioletabsorber is optional. However, for best results, said additives shouldbe employed in conjunction with the antioxidants of this invention,especially the secondary antioxidant. These supplementary additives maybe used in the amount of from about 0.05 to about 5% each, andpreferably from about 0.1 to about 2% by weight of the substrate.

Besides activity in the oven ageing test, the novel antioxidants of thepresent invention are characterized by excellent color values (nodiscoloration during the oven ageing test) and good gas fadingproperties.

The present antioxidants are useful in protecting synthetic polymerssuch as polypropylene against oxidation in air, thermal degradation ordeterioration by including in such substances, a stabilizing amount ofthe antioxidant which will vary between about 0.01 and 5% andpreferably, from about 0.05 to about 1.0% by weight. The antioxidant canbe incorporated into the synthetic polymers using conventionalprocedures. For example, the antioxidants of the present invention areincorporated into the material to be stabilized by any suitable meanssuch as by milling the antioxidant on hot or cold mill rolls, by mixingit in by the use of a Banbury mixer or other well-known devices of thisnature or the antioxidant may be mixed with a polyolefin material in theform of molding powder and incorporated during extrusion or prior toextrusion or during injection molding. The antioxidant may even beincorporated into a solution of the polyolefin material and the solutionmay then be employed for the formation of films, for wet or dry spinningof fibers, monofilament and the like.

The examples set out above are to be considered as illustrative of thepresent invention and are not to be considered as restrictive. It istherefore to be understood that the invention is not limited to thespecific embodiments set out above except as defined in the appendedclaims.

What is claimed is:

1. A composition of matter stabilized against deterioration comprisingan organic material normally subject to deterioration and a stabilizingamount of an antioxidant compound having the formula formula ROCOCH CHS(S)P( s 5)z wherein R is a 3,S-di-t-butyl-4-hydroxyphenyl.

4. A composition of matter according to claim 2 wherein said antioxidantis a compound having the formula:

R0o0oHs(S)P(csH5) R0 0 0 H, wherein R is 3,5-di-t-butyl-4-hydroxyphenyl.

6. A composition of matter according to claim 2 wherein said antioxidantis a compound having the formula:

ROCOCH (CH )CH S(S)P(OC H wherein R is 3,5-di-t-butyl-4-hydroxypheny1.

7. A composition of matter according to claim 2 wherein said antioxidantis a compound having the formula:

ROCOCHS(S)P(OCH5)2 R O C 0 H2 wherein R is3,5-di-t-butyl-4-hydroxyphenyl.

8. A composition of matter according to claim 2 Where in saidantioxidant is a compound having the formula:

R0 0 o CHCHZS(S)P( 002115) R 0 o 0 0H, wherein R is3,5-di-t-butyl-4-hydroxyphenyl.

References Cited UNITED STATES PATENTS 2,876,156 3/1959 Barley et a1.290942 2,578,652 12/1951 Cassady 260942 3,047,459 7/1962 Perini et a1.260941 3,367,870 2/1968 Spivack 26045.95 3,291,809 12/1966 Cyba 26045.8

DONALD E. CZAJ A, Primary Examiner V. P. HO-KE, Assistant ExaminerU.S.CI.X.R.

